Seventh Avenue in Park Slope just got its second Vietnamese sandwich shop — four blocks from the neighborhood’s first place — and not since the Vietnam War has there been as juicy a story of spies, secrets, lies and Vietnamese families torn apart.

At least this time, the collateral damage is delicious.

The newcomer in question — Henry’s — is just four blocks south of the original banh mi joint, Hanco’s.

Of course, it’s not uncommon for competitors to set up shop side by side. It happens all the time with McDonald’s and Wendy’s, Duane Reade and CVS or any number of pizzerias.

But then again, Ronald McDonald doesn’t accuse the girl with the pigtails of stealing his hamburger recipe.

In this battle, however, Hanco Tang is accusing Henry Huynh of stealing his secrets while he worked at Tang’s original sandwich shop on Bergen Street in Cobble Hill.

There’s substantial evidence to bolster Tang’s claim:

• Huynh’s menu is virtually identical — in typeface, in offerings, in almost every detail — to Tang’s.

• Huynh’s sandwiches are almost as identical, offering that delightful Southeast Asian combination of crispy and sweet ground pork, ham, pate, mayonnaise, chili peppers and picked carrots and daikon — all piled high on a fresh baguette, a relic of the days when France controlled Indochina.

• Huynh offers bubble tea drinks, just like Tang.

• Huynh really did work at the Bergen Street Hanco’s — and left under less-than-ideal circumstances.

“He stole the recipe,” Tang told The Brooklyn Paper. “We don’t have proof, but it just disappeared. What they do is almost identical to us and their menu is exactly the same.

“They were still working for me while they were working on opening their store. They were like spies,” he added. “I’m really pissed off. I spent years to set up everything and then they just copied me.”

Naturally, Huynh denied it — though he did admit that he had a falling out with Tang.

“There were difficulties between me and [him], and I wanted to start my own business,” he said.

As for why the menus are virtually identical, Huynh waved that off.

“I was really busy with other things, so I had my friend do the menu,” he said. “I had no idea what it would look like.”

Of course, banh mi fans could be excused for seeing a certain irony to this latest Vietnam War. For all that Tang complains about Huynh, he’s also been accused of being a sandwich swiper himself.

As The Brooklyn Paper reported a year and a half ago, Tang had a Brownstone Brooklyn banh mi monopoly at his original Bergen Street location until a shop called Nicky’s opened around the corner on Atlantic Avenue in 2007.

Nicky’s, you’ll recall, is owned by the Dang family, which owned the seminal Sunset Park sandwich shop, An Dong — where Tang admits he often hung out when was growing up, hoping to pick up tips for an eventual sandwich shop of his own.

When he opened Hanco’s, the Dangs blasted him with much of the same language he now reserves for Huynh — though the Dangs never accused Tang of the kinds of things that Tang is saying Huynh did.

“When Henry was still working for me, one of the other employees purposely made bad sandwiches with cold meat and too much mayo, so I fired him,” Tang said. “Then after I fired him, Henry and his mother quiet and then another girl quit. They all work at Henry’s now.”

Tang suggested that the bad worker was intentionally making poor sandwiches to undermine Hanco’s reputation on the eve of Henry’s opening.

Foodies can be assured that Hanco’s quality is as high as ever. In fact, in a double-blind taste test by The Brooklyn Paper, the Hanco’s sandwich emerged as ever-so-slightly better than Henry’s: the meat a bit juicier and flavorful, the sauce a tiny bit more moist, the bread a bit crispier.

Huynh’s sandwich has the advantage of being 55 cents cheaper — but it’s unclear how long that sale will last.

For now, Huynh said he wanted to remain on the high ground and not fight it out with his former boss. Besides, as in that more famous Vietnam conflict two generations ago, the Americans will ultimately have to choose what side they’re on.

“Competition makes the food better, and our customers will decide who is better,” he said.

The fight is not only being waged in the shops, but on the Internet (of course). The Hanco’s vs. Henry’s smackdown has been the talk of the Brooklynian message board, where lovers of banh mi have picked sides.

“I hope my kids are safe at home when this thing gets settled in the street,” quipped South Slope Suit.